At this stage, it is not known whether the new model will manage to match the outstanding aerodynamic efficiency of the original CLA, which holds the distinction of being the most aerodynamically efficient car ever placed into larger-scale production, with a drag coefficient of just 0.22 in CLA180 BlueEfficiency guise.

The rear doors, like those of the previously spotted shooting brake variant, appear longer than those of the outgoing model, hinting at improved rear leg room and easier entry and exit for passengers.

The new CLA and CLA Shooting Brake will be the fifth and sixth models to use Mercedes’ MFA2 platform, following on from the A-Class, A-Class saloon, long-wheelbase A-Class saloon and recently unveiled B-Class. It supports both front and four-wheel drive and is engineered to accommodate either a torsion beam or multi-link rear suspension.

The CLA joins a range of new Mercedes models that are due to be launched in 2019, including the fourth-generation GLE large SUV and the EQ C electric SUV.

Power for the new model will come from a range of four-cylinder petrol and diesel engines, including a powered-up version of Mercedes’ latest M260 turbocharged 2.0-litre petrol unit in the new four-wheel-drive CLA35 and CLA35 Shooting Brake models from AMG.

A more highly tuned version of that engine with more than 400bhp will also be used to power range-topping CLA45 and CLA45 Shooting Brake models.

Mercedes confirmed the planned introduction of the new CLA and CLA Shooting Brake, as well as an eighth compact model in the form of the GLB SUV, with the issuing of a so-called official product roadmap graphic.

The graphic, part of a presentation announcing the German car maker’s 2018 sales up to the end of September, pinpoints six cars that are set to be unveiled next year.

Joining the CLA, CLA Shooting Brake and the GLB will be facelifted versions of the GLC SUV and GLC coupé, as well as the third-generation GLS.

Details to the four-door CLA remain scarce, although recent prototypes caught it with a distinctly more sporting appearance than the recently unveiled A-class saloon, alongside which it is planned to be produced at Mercedes-Benz’s factory in Kecskemet Hungary, with greater tapering to its front end, a more heavily angled windscreen, greater curvature to its roofline, a shallower glasshouse with frameless doors and a more shapely rear end.

If the prototypes being tested by Mercedes-Benz are any guide, however, the 2019-model-year CLA will be quite a bit larger than its predecessor, with a longer wheelbase set to provide added length to the rear door apertures in a move aimed to ease entry to the rear along with improved rear legroom.

Even less clear is the look set to be adopted by the second-generation CLA Shooting Brake. Like its predecessor, though, it is rumoured to receive a heavily stylised appearance with a sloping roofline and heavily angled tailgate set to prioritise good looks ahead of ultimate load-carrying capacity.

Together, the two models form part of a future eight-model-strong compact car line-up that will also include the new GLB – a rival to the BMW X1 and Audi Q3 – which the Mercedes-Benz roadmap hints will be unveiled during the latter half of 2019, as well as a successor to the GLA that’s set to be launched in 2020.